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Magnetic resonance imaging (MRI)

What you need to know about this test

Patient Education
Published Aug. 6, 2018
• Reviewed by a UI Health Care Provider
on Dec. 9, 2025

What is it?

Magnetic resonance imaging (MRI) is a test that uses a magnetic field and pulses of radio wave energy to make pictures of organs and structures inside the body. When you have an MRI, you lie on a table, and your body is moved into the machine. An image is then taken of the body part being studied.

How can I get ready for my test?

If English is not your first language (the language you speak best), bring a family member or friend that can help interpret. You can also ask for an interpreter at no cost.

If you need special prep for your test, we will give you a handout with more information.

The MRI machine acts like a strong magnet for some metals. Tell your care team before you schedule the MRI if you have any metal in your body from pacemakers, hearing devices, or past surgeries or accidents.

Before your test, tell your care team if you are:
  • Pregnant or may be pregnant.
  • Allergic to MRI contrast dye. Be sure to tell your care team about these allergies before the day of the test. They may have you take medicine the night before and morning of their test.
  • Afraid or anxious in tight spaces? You may need medicine to help you relax. This must be arranged before your test.
Food
  • You may eat and drink before your test unless you are getting sedation or anesthesia.
  • If you have any other test(s) on this same day where you are told not to eat or drink, follow those instructions.
Driving
  • You will need somebody to drive you home after your test if you take a sedation or relaxation pill (like Ativan® or Xanax®) or a medicine for an allergy, such as diphenhydramine (like Benadryl®). You cannot drive for 24 hours after taking these medicines.

What to expect

  • The test often takes 15 to 45 minutes. Sometimes it can take up to 2 hours.
  • When you come for your test, you will fill out an MRI screening form. This screening form will ask about any metal objects inside your body.
  • You will change into a hospital gown and pants for your MRI.
  • You will need to take off jewelry, hairpins, watches, glasses, hearing aids, nonpermanent dentures, and wigs (if they have metal) before your test. You must also empty your pockets.
    • You will be given a locker to use for your things during the test.

How is the test done?

  1. You may have contrast materials (dye) put into your arm through a tube called an IV. The dye might feel cold or like it is leaking when put into the IV. You may have nausea with contrast. Tell the technologist if you feel sick.
  2. You will lie on a table that is part of the MRI scanner.
  3. The table will slide into the space that has the magnet.
  4. We will give you an emergency ball during the scan.
    • This is for your safety. If you feel breathless, have chest pain, are dizzy, or have a contrast reaction, squeeze this ball right away. It will let the technologist know that you need help.
  5. Inside the scanner you will hear a fan and feel air moving. You may hear tapping, thumping, or snapping noises. We may give you earplugs or headphones to lessen the noise.
  6. You need to hold still during the scan. You might be asked to hold your breath for short periods.
  7. You may be alone in the scanning room. A technologist will watch you through a window and talk with you during the test.

What are the risks of the test?

  • Dye with a chemical element called gadolinium may be used in this test. For most people, the benefit of its use in this test outweighs the risk. Be sure to tell your care team if you are on dialysis or are pregnant.
  • You may have a reaction to the dye. This may cause rash or tight or itchy throat, mouth, lips, or eyes.
  • You will need medicine if you have a reaction. Tell the technologist or care team right away if you feel those symptoms.
  • If you breastfeed and are worried if the dye is safe, talk to your care team. Most experts believe that very little dye passes into breast milk and even less is passed on to the baby.